The second-generation racer has been employed as reserve driver in support of George Russell and Lewis Hamilton.
It’s a position he’s held for the past two seasons, since losing his F1 race drive at Haas to Nico Hulkenberg.
However, he’s elected to leave the operation in pursuit of a return to racing.
“I am grateful to Toto and the entire Mercedes-AMG Petronas F1 Team for the insight I have gained over these two years,” he said.
“They have undoubtedly made me a more experienced racing driver because I have got to know the engineering side better.
“But watching these cars race and not sitting in the cockpit myself is tough.
“I want to get back to focusing 100 percent on racing. I want to be fully committed to the sporting side of motorsport.
“Ultimately, it is racing that you want to do as a driver, it is racing that gives you that feeling you love.”
Schumacher was briefly connected to Mercedes as a potential replacement for Ferrari-bound Hamilton.
However, he was overlooked for that opportunity and the drive at Alpine that eventually went to Jack Doohan.
Schumacher competed as part of Alpine’s World Endurance Championship team in 2024, in conjunction with his F1 role with Mercedes.
Mercedes team boss Toto Wolff paid tribute to the German.
“Mick’s hard work, diligence, and determination in his role as reserve driver has been vital for the team over the past two years,” said Wolff.
“From his work in the simulator, testing of various cars, and being part of the trackside team, we couldn’t have asked for any more from him.
“From day one, he fitted into the team with ease and has become an incredibly well-liked colleague for everyone at Brackley and Brixworth.
“However, Mick is first and foremost a racing driver,” he added.
“We have seen from both his time in F1, and this year with his performances in the World Endurance Championship, that he is a racer of an incredibly high calibre and one that deserves to be competing in the very best championships.
“As he moves on to his next challenge, I would like to thank Mick personally for his contribution to our team and we all wish him the very best in his future endeavours.”